1. Field of the Invention
The consumption of improperly prepared poultry products has resulted in numerous cases of human intestinal diseases. It has long been recognized that Salmonella spp. are causative agents of such diseases, and more recently Campylobacter spp., especially Campylobacter jejuni, has also been implicated. Both microorganisms may colonize poultry gastrointestinal tracts without any deleterious effects on the birds, and, although some diseased birds can be detected, asymptomatic carriers can freely spread the microorganisms during production and processing, resulting in further contamination of both live birds and carcasses.
2. Description of the Prior Art
Better control measures are needed to minimize the spread of these and other human enteropathogenic bacteria, and the most promising approach to achieve this end has been to decrease the incidence and level of microorganism colonization in poultry gastrointestinal tracts.
An effective means for decreasing colonization of chickens by Salmonella was described by Nurmi and Rantala (1973) and is known as competitive exclusion (CE). The chicken's indigenous intestinal flora plays a significant role in protecting it against Salmonella colonization, and it was found that preparations of subcultured intestinal contents from mature, healthy chickens conferred protection to young chicks whose microflora had not yet been established. Administration of undefined CE preparations to chicks speeds up the maturation of the gut flora in the newly-hatched birds and also provides a substitute for the natural process of transmission of microflora from the adult hen to its offspring. The cleaned and disinfected facilities of contemporary broiler houses do not provide the naturally-occurring microflora which had been provided by hens in days past. Snoeyenbos et al. (1982) developed a technique designed to reduce salmonellae in poultry where the source of CE microflora was lyophilized fecal droppings which were propogated by anaerobic culture. Mikkola et al. (1987) used intestinal fecal and cecal contents as a source of CE microflora. Treatment with their culture required media to be anaerobic and pH balanced. Neither of these CE treatments addressed Campylobacter jejuni.
Since CE was known to be effective against Salmonella, a similar method for the control of Campylobacter was investigated by Stern et al. (1988). It was found, however, that treatment with CE preparations, such as described by Nurmi and Rantala (1973), Snoeyenbos et al. (1982) and Mikkola et al. (1987), did not affect Campylobacter colonization. After treatments with five different CE cultures, colonization was observed after challenge by Campylobacter in 81 of 84 chicks, and 45 of 46 control chicks. Shanker et al. (1990) confirmed these observations (Shanker et al. 1990. Epidemiol. Infect., vol. 104, pp. 101-110).
In a subsequent investigation, compositions of mixtures of Salmonella and Campylobacter were administered to day-old chicks. It was believed that the two microorganisms might compete with or otherwise antagonize each other, thereby reducing both populations (Stern et al., 1991). No competition or antagonistic effect was observed, however.